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Building The Godzilli 16 Hull

After the panels were scarfed, I was gone for a week so the panel and bulkhead lofting had be done as well as most of the bulkheads set up on the strongback. The strongback is a 2x6 structure I have used for years, actually it's 6' sections that are screwed together for the desired length. A laser level is used to get it level with small wedges to shim up the low areas. After it has been leveled spray foam is used to hold the wedges in place and to hold the strongback in place.

The bulkheads are lofted out with the "baseline" being the top of the strongback. The plywood is not always big enough to rest on the strongback so filler pieces are made and sit on the strongback at each bulkhead station to get the bulkhead at the desired height. A 3/4" hole is drilled at the waterline and on centerline. When all bulkheads are installed, a string is run through the holes, centered on the first and last bulkhead hole. If the setup went properly, the string should be centered in all the holes. Of course it never happens that way and small adjustments need to be made the bulkheads that are out of alignment.

Plywood Stitch and Glue Construction

To make a rounded stern a "mold" is needed. The bottom panels are part of the mold, and the transom harpin it the other part. In the picture below there are two longitudinals screwed to the aft bulkhead and the transom harpin is screwed up to the longitudinals and the aft bulkhead. This structure needs to be supported from the floor or strongback so the aft bulkhead does not bend.

{Plywood Stitch and Glue Construction

The bottom panels are stitched along the keel and set on the bulkheads. When they were lofted out, they were also marked where the bulkheads land. The chine corners of all the bulkheads should not extend out beyond the bottom panels or it will push out the side panels when they are installed. If a chine corner is to wide, trim it back by drawing a line from where it is needed to the actual sheer point. The side panels only need to touch the bulkheads at the shear., at the chine the shape is determined by the bottom panels. The shape of the hull is determined by the points on the bulkheads at the keel, the chine and sheer. It is not necessary that the entire edges of the bulkheads come in contact with the hull panels everywhere. Panels can always be shimmed out but it can be difficult to trim bulkheads when the panels are on.

Plywood Stitch and Glue Construction

The side panels are only stitched on with a couple of stitches at the first 12". Because the bottom panels and side panels are almost at a 90 degree angle, I used construction screws to fasten the panels together keeping the bottom edge of the side panel flush with the bottom face of the bottom panel. On the bow I screwed blocks to each side and used a clamp to hold the bow together. Make sure that the bow at the sheer is kept on centerline and does not shift to one side or the other. Again, construction screws were used to hold the bow together and the clamps were pulled. Run a batten around the hull to check for fairness and tab. When I tabbed, I also glassed the bulkheads to the side panels with two layer of 12 oz. biax and two layers of tooling cloth.

Plywood Stitch and Glue Construction

Because of the rounded stern the side panels terminate at the aft bulkhead. Thinner plywood will be needed to make that bend. I used 1/4" and it was still to stiff to make the bend, perhaps a softer species like Okoume would have made the bend, but I did not have it to try so I scored the plywood I had every 2" almost halfway through. All the pieces are dryfit first starting with the two side pieces (48" wide each) then the aft piece is cut to fit. On the second layer start with the aft piece (48" wide) and then fit the side pieces. This accomplishes two things, first the joints are well offset and it also has the cuts in the plywood running in slightly different directions.

Plywood Stitch and Glue Construction

The first layer was more difficult to fit because with the cuts facing out the plywood will break easier. With the cuts facing in, as with the second layer, it is easier to bend without breaking. After both layers of 1/4" were dryfit I did a rough trim at the chine and sheer.

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When Gluing up the stern I did it so I could remove it. The first layer was screwed in with as few screws as needed to hold it in place and I applied clear packing tape to all the surfaces of the hull that the stern pieces might get glued to from epoxy squeeze-out.

I troweled thickened epoxy into the all the cuts in the plywood and then rolled a coat of slightly thickened epoxy to both faces that were glued together. I was not to concerned about making sure the 1/4" plywood was well fastened to the hull, but getting the two layers screwed tightly together was important. I ran a lot of screws through the two layers to get them to suck together and made sure the butt joints were well fastened on each side of the joint. Remember there are also two butt joints on the first layer that need to be addressed as well as the two on the outer layer. Don't worry about all the screw holes, they can be easily filled later.

After the epoxy has cured pull all the screws. The few fasteners that were put in the first layer will need to be tore lose from the hull and can then be pulled through the inside layer of plywood. All the minor damage the fasteners cause will be filled an buried under epoxy and glass later.

Plywood Stitch and Glue Construction

Excuse the poor images below, hope you can follow along.

Before I pulled the stern off, I scribed the harpin location and also ran a batten along the sheer of the side panels and on the first couple of feet of the stern and marked the sheer line on the stern piece. By scaling off the plans I got measurements of the location of the sheer above the harpin and screwed fasteners from the inside out. at those random locations. I then ran a batten around the outside of the stern resting it on the screws, this is the sheer line and should match up on each end with the one that was marked earlier from the side panel sheer line. If it is off a bit adjust the sheer line on the stern to match the actual sheer of the side panels. The reason I made the stern removable is so I could get a good look at it in the upright position. It makes it so much easier to fair when you are not standing on your head.

Now that the sheer is fair dryfit the piece and make sure it all checks out, trim as necessary. The stern gets glued to everything but the harpin. The harpin needs to be removed after roll-over so the compartments can be glassed and sealed. Put clear packing tape around the edge of the harpin. All other mating surfaces need to be wet out with clear epoxy and then peanut butter added, screw in place.

Plywood Stitch and Glue Construction

Because the side panels and transom were added separately, the butt joint between them is the weak spot of the hull.

I screwed a piece of plywood to the hull as a straight edge to remove 1/4" of material with a router. I went about 5" on each side of the joint. A piece of 1/4" plywood was fit into place then glued and screwed. This joint will also get glassed on the inside on each side of the bulkhead.

Plywood Stitch and Glue Construction



This is a Devlin design, for more information on this design and others offered by Devlin Boat, go to devlinboat.com

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